Combustion method



C. J. HUBER COMBUSTION METHOD Feb. 16, 1932.

Filed March 2. 1927 Feb. 16, 1932.

c. J. HUBER COMBUSTION METHOD Patented Feb. 16, 1932 UNITED STATE-s PATENT `OFFICE l CHARLES. J. HUBER, OF BALTIMORE, MARYLAND, ASSIGNOR F `ONE-HALF TO FLYNN AND ,EMRICH COMPANY, OF BALTIMORE, MARYLAND, A CORPORATION 0F MARY- LAND Application led Marchv 2,

In the development of stoking methods and apparatus, particularly Within the last few years which have witnessed the enactment of smoke ordinances andthe rapid advance in fuel prices, the trade has demanded the maximum efficiency in heat and power production from a given amount of coal and the reduction of smoke to the greatest possible extent. The achievement of these ends is dependent upon 1o the accomplishment of a single result, i. e.,

20 tion relates, and natural, draft, have advantages as to simplicit vand cheapness and ease of operation which ave prevented their displacement by the underfed type and the use of forced instead of natural draft, but previously to the development of the present method of combustion the overfed type has proved deficient in the points just emphasized. It has been particularly dilicult in the overfed type to achieve complete combustion of the fine particles of carbon and vapors and gases given oif by the fuel, principally as it is heated up to the temperature of combustion, but also during combustion, so that the escape of a certain amount of smoke and the lossof a considerable proportion of the actual heat content of the fuel has been unavoidable.

The fuel most commonly used in boiler furnaces is bituminous coal which may be termed a two element fuel consisting of vaporizable matter and carbon. The necessity for the admission of air from above as well as through the fuel bed in the burning of such fuel is well recognized, the air admitted through the fuel bed being known as primary air and that admitted above the fuel as secondary air. The invention relates to a more efficient andl scientific method of burning this fuel having particular reference to the admission of primary and secondary air and the combination of both with the vapor- .v conBUsTIo'N METHOD 1927. serial nt. 171,939.

izable portions of the fuel to produce substantially complete combustion, resulting in the maximum of heat and developing the highest capacity of the furnace with the use of natural draft, it having been proven in actual practice that by the use of this method a thirty to forty percent increase of the steaml output from a given boiler can be obtained without alteration of the stack or otherwise increasing the draft or the size of the-furnace'.

The invention may be aptly termedfa tw cycle method of handling a two element fuel. In accordance with the method of theinvention Vthe fuel is first heated, separa-ting the volatile portions of the fuel from the solid and passing air over the fuel thus heated mixing air with the vaporized portions of the fuel at the instant of distillation and in the correct proportions. The air and gases being at this time, i. e., at the time of mixing, at a temperature above the kindlin temper ature of the mixture are complete y burned and the solid fuel is ignited by the burning of the vaporized materials before it is deposited on the fuel bed. .l

The ignited solid fuel still containing a portion of the vaporizable material is then deposited on to of a bed of burning fuel. Over this a dra of secondary air is passed,- mixing with the remainder of the gases distilled by contact of the newly fed. fuel with the high temperature of the fuel bed, effecting complete combustionl of all vaporizable material. The fuel bed composed of burning solid fuel is fed gradually backward, agitated and aerated by the admission of primary air from below so that all the fuel comes in contact with the primary air and there is a surplus of unburned heated air to complete the combustion of the gases over the l'ire, the passage of the same through the fuel being facilitated by agitation and the fine ash being dropped as the fuel progresses backwardly through the furnace, the clinker and unburnable solid matter being deposited at the rear and being dropped at intervals into the ash pit.

In the accompanying drawings I have illustrated an apparatus by means of which the method of the invention may be practiced t0 cordance with the method.

' each of which is used to indicate the same orv Figure'2 is a section transverse to the plane of Fi ure 1 and looking forwardly, i. e., to the le t in Figure 1.

Referring to the drawings by numerals,

similar parts in the different figures, the apparatus as shown comprises a furnace structure 1 including an arch structure 2 at the front extendin .across the furnace and composed as to its ottom portion of heavy blocks 3 of fire brick or resistive ceramic material soV arran ed that the bottom face 4 of the arch exten supwardly and to the rear from `the feed opening 5. Beneath the feed openingr is the coking shelf 7, also of heavy ceramicI resistive material as fire brick, the members 3 and 7 serving as heat storing or reflecting members which receive heat by direct radiation from the fire, store it and transmit it to the fuel.

The feed opening 5 and the hopper 8 preferably extend across the entire width of each heating unit or furnace so as to form a layer of fuel at 9 on the coking shelf and a curtain of fuel at 10 where the ignited fuel drops from the shelf, the curtain of fuel and the shelfextending across the furnace ex osing the greatest possible area of fuel sur ace to the action of air currents and to the passage of the air currents through the burning fuel as hereinafter described. The fuel h eate and ignited, as hereinafter described, is fed from 'the shelf by the operation 'of the coal pusher 11, which is reciprocated by means of any suitable gearin actuating the crank 12 and connecting ro 14 which is in turn connected to the pusheiyas shown, or in any suitable manner. I

The illustration, Figure 1, includes intransversev air lpassage 15 in the arch above the fire brick heat storing and radiating members 3, the air passage being heated by the waste heat from the furnace and led downwardly and forwardly from theI transverse passage 15 into fore and aft passage 16 directly over the fire bricks and forwardly from this passage into vertical which it is discharged throug air inlet opening 18 into the furnace cavity immediately above and in contact with theA fuel on the cokino shelf 7. I

In igure 1 I have shown air openings 27 and 28 beneath the coking shelf and forward of the lower rear edge 19 thereof and particularly forward of the front portion 20 of the bed of burning fuel on the grate whereby 'air is admitted forward of the fuel bed and beneath the coking shelf andl passed through assages 17 by` the more or less variable and intermittent curtain of freshly ignited fuel at 10 and in contact with the fuel pile or front 2O of the fuel bed, which consists of freshly ignited fuel at 21 just dropped on the burnin and partially consumed fuel bed, the air eing thus combined with the particles of solid carbon which are liberated from the freshly ignited coal in the form of smoke and consuming the same, and the air not thus burned being heated and passing upwardly in combination with the combustion gases in the complete burning of which the supply of air thus admitted combines with and assists the supply of air admitted from above the shelf.

The apparatus further includes a grate 30 which is preferably inclined downwardly and to the rear, as shown, and composed of rocking bars 32 which are preferably of segmental cross section, being pivoted by means of journals 33 at the vertex of each segment and having arcuate outer swinging surfaces 34 in Contact with, or substantially in contact with, the sharply curved rear surface 35 of the next bar to the front, which curves are concentric with the axis of the bar. These bai-s are slotted and are arranged in series of alternate bars, each bar having a depending arm 36 which is pivotally connected to a sliding link 37, there being one of such links for each set of bars, all the bars ofeach set being thus pivotally connected to the same sliding link 37.

The two sets of bars are oscillated alternately either at regular intervals by means of a continuously operating motor and selective timing mechanism, indicated in a general way at 40, and connecting rods 42, or the apparatus may be -operated manually, the links being for this purpose connectedto any suitable actuating mechanism, as the manually operated actuating operating means shown at .41, the member 41being a socket to receive a hand lever. Beyond and somewhat below the rear and lower end of the grate is a drop bar 43, hinged at the forward end at 44 and supported at the rear on a link 45 which, in the normal position, is substantially upright, being pivotally connected at its upper end at 46 to the rear edge of the drop bar and pivotally connected at its lower end to a third sliding bar 47. By pulling the forward end of the bar 47, sliding it in a forwardand slightly upward direction, the drop bar is swung downwardly drop ing the clinkers and accumulated material into the ash pit.

In the practice of the method which is the subject of the invention, it being assumed that the stoking grate or stoker is covered with a thick bed of burning fuel, the hopper 8 is kept filled with a supply of fuel which is ordinarily bituminous coal, the same being fed through the feed opening 5 at the bottom of the hopper from time to time at the will of the operator, orv otherwise, or in any suitable manner as by the actuation of the pusher 11. The feeding operation, as described, it being noted that the advanced position of the pusher is well forward of the rear edge of the fuel supporting surface of the'v coking shelf, maintains at all times a supply of fuel at 9 on top of the coking shelf. The fuel on the4 shelf remains undisturbed between the strokes of thel fuel pusher, the re ularpractice being to actuate the pusher fbr a single stroke at intervals dependent on the amount of fuel consumed.

The portion of the fuel thus fed to the shelf and remaining thereon from one stroke to the next of the fuel pusher is exposed not only to the radiation of the fire, but to the heat stored in the heavy fire brick shelf 7 wh ich is transmitted to the fuel by conduction the shelf being during full operation ofthe furnace maintained at a white heat. and to the heat of the arch, which is an efiicient heat storing member, as described, which heat is transmitted to the coal by radiation, it being understood that the arch is also normally maintained at a White heat by the radiation of the lire to which it is directly,

exposed. While each charge of fuel thus supported on the arch is exposed to the highest temperatures which can be resisted by resistive solid materials, as the lire brick composing the shelf, without destruction, it is further subjected to the action of a draft of air entering by the passages 17, the air current being heated by waste heat from the upper and outer portion of the arch above the heat storing members 3. The high temperature to which the coal is thus subjected results in quick distillation of the volatile materials which are given off together with considerable quant-ities of finely divided solids, ordinarily termed smoke, resulting from the destructive distillation of the tarry portions of the fuel.

. In the previous practice the presence of green coal on the fire with an insufficient supply of air caud these products to be passed up the flue, resulting in the discharge of smoke and noxious gases.

` In accordance with the method of the present invention, the finely divided solids and gases are immediately consumed by mixingl with the draft of hot air introduced through the passages 17, the Whole being above the temperature of ignition for the gases and vapors the mixture is immediately burned. There is preferably a sufficient excess of -air over that required for this purpose to ignite the partially coked fuel left on the shelf, the fuel being above the kindling temperature. `As particularly illustrated in Figure 2, thehoppe'rs, coking shelves'7 and lthe layer and curtain of fuel, extend the full width of the furnace. The supply of fuel on the shelf having been thus partially coked and ignited and the pusher having been withpusher being again advanced after a convenient interval corresponding to the heat being generated and, therefore, to the fuel burned, the new supply of green fuel immediately in front of the pusher displaces the partially coked and ignited fuel on the shelf and. causes a considerable portion of the latter to pass over and fall from the rear edge of the shelf onto the fire, forming the curtain 10 ,already referred to. In this connection it is important to note that the stream or curtain of partially coked and burning fuel thus dropped on the fire extends across the entire width of the furnace. As the fuel falls from tbe coking shelf in the ignited and highly heated condition described, it is subjected to a further draft of pure unburned air entering from beneath and forward of the coking shelf, or at least forward of the rear lower edge 19 of the coking shelf and the fuel pile. This air enters either from the ash pit or through the fire door by way of passages 27, 28, the fire door being mainly for emergency access to the furnace and insurance against shut down. The air thus admitted passes through the curtain and over the coal pile, coming in contact with each piece of coal and the latter being in a highly eated condition the air minglin with the heated gases and suspended soli particles, assures complete combustion of the gases and suspended solids, eliminating smoke and noxious fumes. l It is important to note that the air draft as admitted passes in close contact with the front of the pile of burning fuel on the grate at 20, taking up and lmingling with and burnin in the high temperature of the furnace, t e suspended solids and volatile matter given off on this surface of the fire, which is necessaril composed almost entirely of newly admitted fuel. which is, however, partially coked and fully ignited, as aforesaid.

The subjection of the highly heated fuel on the coking shelf by direct radiation and by conduction and radiation from the coking shelf,. to a draft of heated air from above whereby it is ignited and then dropping it on top of the fire subjecting it as it fal s and when itirst lands on the fire to a further draft of air from beneath the coking shelf, partially cokes and completely ignites the fuel, deprivingy it of most of its volatile mat- 'ter and completely burns the gases and susfurther-facilitate the admission and passagel of air therethrough by dropping the ashv ati.; a-ll .pointson the grate, the unburnable matecokin progresses,:but thefi're its -continually broken.

admitting thev air'- from beneath the grate through the Stoker bars".to` all' points in the fuelk bed-"whereby the process of combustion is'ca'rried on' uniformly throughout the `body oflthexfuel .on 'tlie 'grate. Theaction of the bars also serves vin breaking up the fuel to rial', asl clinkers, being moved onward down thefgrate and finally deposited on the drop bar @43 from whichrthey are dropped from J timeto time into the ash pt--completely disposing of l all materials introducedas and withthe-fuel..`l

llVhile many efforts have been made to obtain l complete combustion, eliminating smoke.- and obtaining the` greatest possible ortion V ofthe heat actually contained in the uel, andfwhile it is understood that the accessl ofai'r or oxygen to every particle of the fuel, solid, vaporous and gaseous, is necessary for complete combustion,'and many efforts have beengmade toA accomplish this result, it is beli'vedthat ypreviously to the present. inventionno method has been' devised whereby by feedin coal to the top of the lire, and particular with natural draft, complete burning of the finely divided suspended solids or smoke, gases and burnable solid unvaporizable materials has been attained, and the result in the present instance'is believed to be due to the combination of steps whereby the fuel' is highly heated on the coking shelf by the radiation of heat stored in the arch, the conduction and" radiation of heat stored in thecoking shelf-and' the direct radiation of heat 'from the lire, and at the same time subjected to a draft of hot air and, as it is droppedon the fire, in the highly heated and ignited lcondition is further subjected to a draft of Vair from forward and beneath the shelf which is passed throu h and over t e fuel as it 'falls and immediate y after it has landed on the fire, whereby a fuel bed composed entirely of burning coal containing no 'green' fuel at 'any time, is maintained. The'c'ontinual advancement and breaking of the lire providing forithe admission of air atall points-and the dropping'ofthe ashl contribute :to andimportant' extent to the whole :resulti whereby complete combustion' I have thus described specifically and Ving detail a method of combustion in accordance in order that the method of applying the in.Il

vention may be clearly understood, however,

the specific terms herein areused descriptively rather than ina limltmg sense, the scope of the invention being defined 1n the.

claims. ,v

'jWhat I claimasnew and desire to secure byLetters Patent is:

1. The method of burning -coal' in a furnacewhich consists in maintaining a bed of completely ignitedand burning' fuel, break- .ing the bed throughout its extent continually and passing air through it, dropping the fine unburnable residue, presenting a supply of green fueland maintaining the same Within the furnace above the fire at the forward end and extending across the entire width of the fuel bed at the front, heating the same by conduction, radiation andy reliection from the fire to a temperature above the kindling point of the fuel and driving off gases and vapors therefrom, admitting a. supply of heated air above the fuel supply thus maintained and passing it over the fuel as it is heated, mixing the same with the gases and.

vapors given olf from the newly heated fuel supply at a temperature above the point of ignition of said vgases and'vapors, burning the vsame and igniting the fuel su ply thus presented, dropping the supply o burning fuel on the front end of the said bed of burning fuel von the fire across the entire width of the furnace, admitting air from be low said fuel supply forward of the fuel bed and passing the air over the forward end of the fuel bed in contact with the recently deposited burning fuel and through the said ropping fuel causing the air to pick up 'and .mingle with the gases and finely' divided soli matter being released from the newly deposited 'burning fuel, burning the gases and completing the ignition of the. fuel whereby a bed of fuel, all of which is fully ignited, is maintained throughout the length of the fire. l

2. The method of burning coal in a furnace whichconsist's in maintaining a bed of completely. ignited burning fuel, presenting` a supply of green fuel and maintaining the same within the furnace above the lire at the forward end, heating the same above the kindling point of the fuel by the conduction, radiation and reflection, from the fire thus driving oil' the gases and vapors therefrom, admitting 'a supply of heated air above the fuel supply thusmaintained and passing it over the fuel as it vis heated, mixin the air with the gases and vapors given olf rom the newly heated fuel supply at a temperature above the point of ignition of said gases and vapors, thereby burning the gases and igniting the fuel supply and dropping the supply of burning fuel on the front end of the bed of burning fuel and moving the 'ned of bunk ing fuel backward in the furnace as combus tion progresses.

Signed by me at Baltimore, Maryland, this 28th day of February, 1927.

CHARLES J. HUBER. 

